Abstract
The China Experimental Fast Reactor (CEFR) is a small, sodium-cooled fast reactor with 20 MW(e) of power. Start-up tests of the CEFR were performed from 2010 to 2011. The China Institute of Atomic Energy made some of the neutronics start-up-test data available to the International Atomic Energy Agency (IAEA) as part of an international neutronics benchmarking exercise by distributing the experimental data to interested organizations from the member states of the IAEA. This benchmarking aims to validate and verify the physical models and neutronics simulation codes with the help of the recorded experimental data. The six start-up tests include evaluating criticality, control-rod worth, reactivity effects, and neutron spectral characteristics. As part of this coordinated research, the IAEA performed neutronics calculations using the Monte Carlo codes Serpent 2 and OpenMC, which can minimize modeling assumptions and produce reference solutions for code verification. Both codes model a three-dimensional heterogeneous core with an ENDF/B-VII.1 cross-section library. This study presents the calculation results with a well-estimated criticality and a reasonably good estimation of reactivities. The description and analysis of the core modeling assumptions, challenges in modeling a dense SFR core, results of the first phase of this project, and comparative analysis with measurements are presented.
Highlights
Several fast-reactor experiments have been performed in the past several decades in various countries [1], only a few neutronics benchmarks are available [2]
The start-up test was initiated with a core loaded with 79 mock-up fuel subassemblies consisting of stainless steel (SS) instead of fuel rods in the fuel positions and all the control-rod subassemblies, which were right above the fuel region
The temperature coefficients are negative. This situation is attributed to the following: (1) an expansion of the fuel leads to a decrease in its density, (2) radial expansion of the cladding affects the decrement of the sodium volume, (3) the sodium volume between subassemblies and increased core size increases owing to the radial expansion of the grid plate, and (4) the sodium density decreases because the increase in temperature increases the leakage and leads to a reduction in reactivity [15]
Summary
Several fast-reactor experiments have been performed in the past several decades in various countries [1], only a few neutronics benchmarks are available [2]. The. China Institute of Atomic Energy (CIAE) proposed some of the neutronics start-up-test data for the International Atomic Energy Agency (IAEA) benchmark within the scope of the IAEA’s coordinated research activity [3]. The coordinated research project (CRP) on “Neutronics Benchmark of CEFR Start-Up Tests” was launched in 2018. The objective of this benchmark is to validate and verify the actual physical models and neutronics simulation codes by comparing calculation results against collected experimental data. The China Experimental Fast Reactor (CEFR) is a small, sodium-cooled fast reactor (SFR) It has a core with a high neutron leakage due to its small size and is fueled with uranium oxide (UO2 ).
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